A sewing machine for performing twin overedging and seaming in one high-speed operation is disclosed in U.S. Pat. No. 4,546,716 (Babson et al) issued Oct. 15, 1985 and assigned to the assignee of the present application. The disclosed double overlock seamer is used for stitching the legs of a pair of pants or a skirt. It stitches the seam and overedges the free edge of each ply in a single operation.
The two fabric plies of a pant leg that are fed to the sewing machine for stitching are normally maintained in alignment by the operator. They must be maintained in alignment not only with each other, but also with the sewing machine workstation to produce satisfactory results. When the fabric becomes misaligned, it is necessary for the operator to temporarily stop the machine and correct the alignment. Such stoppage is, of course, undesirable from a productivity viewpoint. Furthermore, it is not always easy to determine exact alignment visually because the edge of the lower ply may be hidden under the upper ply. A further difficulty arises from the fact that the upper and lower plies of a pant leg do not necessarily have the same width. When this occurs, alignment of the upper and lower plies becomes even more difficult, particularly after one side of the pant leg has been stitched. The wider ply must then be bunched up in order to align the plies for stitching of the other side.
It is a general object of the present invention to provide methods and apparatus for automatically aligning fabric with a sewing machine workstation.
It is another object of the present invention to provide methods and apparatus for automatically aligning upper and lower fabric plies with each other and with a sewing machine workstation.
It is a further object of the present invention to provide methods and apparatus for sensing displacement of a fabric edge from a desired alignment line and for guiding the fabric edge toward the desired alignment line as it is advanced toward a sewing machine.
It is still another object of the present invention to provide methods and apparatus for automatically aligning fabric with a sewing machine which are low in cost and easy to operate.